I have tried most of the advice on askubuntu and other sites, usb_storage enable to fdisk -l. But I am unable to find steps to get it working again.

sudo lsusb results

Bus.... skipped 4 lines
Bus 004 Device 002: ID 413c:3012 Dell Computer Corp. Optical Wheel Mouse 
Bus 005 Device 002: ID 413c:2105 Dell Computer Corp. Model L100 Keyboard 
Bus 001 Device 005: ID 8564:1000

sudo dmseg | tail reports

[   69.567948] usb 1-4: USB disconnect, device number 4
[   74.084041] usb 1-6: new high-speed USB device number 5 using ehci_hcd
[   74.240484] Initializing USB Mass Storage driver...
[   74.256033] scsi5 : usb-storage 1-6:1.0
[   74.256145] usbcore: registered new interface driver usb-storage
[   74.256147] USB Mass Storage support registered.
[   74.257290] usbcore: deregistering interface driver usb-storage

fdisk -l reports

Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048   972656639   486327296   83  Linux
/dev/sda2       972658686   976771071     2056193    5  Extended
/dev/sda5       972658688   976771071     2056192   82  Linux swap / Solaris

I think I need steps to install and get usb_storage module working.

Edit : I tried sudo modprobe -v usb-storage reports

sudo modprobe -v usb-storage
insmod /lib/modules/3.2.0-48-generic-pae/kernel/drivers/usb/storage/usb-storage.ko 

Edit :

jsiddharth@siddharth-desktop:~$ sudo udevadm monitor --udev
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing

UDEV  [4757.144372] add      /module/usb_storage (module)
UDEV  [4757.146558] remove   /module/usb_storage (module)
UDEV  [4757.148707] add      /devices/pci0000:00/0000:00:1d.7/usb1/1-6 (usb)
UDEV  [4757.149699] add      /bus/usb/drivers/usb-storage (drivers)
UDEV  [4757.151214] remove   /bus/usb/drivers/usb-storage (drivers)
UDEV  [4757.156873] add      /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0 (usb)
UDEV  [4757.160903] add      /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9 (scsi)
UDEV  [4757.164672] add      /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9/scsi_host/host9 (scsi_host)
UDEV  [4757.165163] remove   /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9/scsi_host/host9 (scsi_host)
UDEV  [4757.165440] remove   /devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host9 (scsi)

Narrowing down more : Seems like I need usb_storage to load as a module

jsiddharth@siddharth-desktop:~$ lsmod | grep usb
usbserial              37201  0 
usbhid                 41937  0 
hid                    77428  1 usbhid

Still no usb driver mounted. Nor does a device show up in /dev. Any step by step process to debug and fix this will be really helpful.